Dominant Spoilage Bacteria Research Articles

Identification of dominant spoilage bacteria in sea cucumber protein peptide powders (SCPPs) and methods for controlling the growth of dominant spoilage bacteria by inhibiting hygroscopicity

Previous studies have found that high active sea cucumber peptide powders (SCPPs) have relatively significant hygroscopic properties. Problems such as liquefaction, altered taste, and decreased activity are observed owing to the hygroscopic nature of SCPPs. Therefore, to develop a new method for accurate, rapid analysis and identification of dominant spoilage bacteria due to hygroscopic SCPPs, we placed SCPPs in 75% RH and 25 °C to monitor the microbial genera and species in samples stored for 90 days in this highly hygroscopic environment. The antioxidant activity of SCPPs stored for 90 days was significantly lower than that of the nature SCPPs (P < 0.05). The hygroscopic nature of SCPPs resulted in the growth of dominant spoilage bacteria. Bacilli (45.89%) were the dominant bacteria at 5 days of storage in a highly hygroscopic environment. Bacilli (41.35%) and Gammaproteobacteria (40.96%) were the dominant bacteria at 15 days of storage in a highly hygroscopic environment, and the number of unidentified Cyanobacteria (20.06%) was sharply reduced to 0.04% (P < 0.05). The deterioration of SCPPs in the highly hygroscopic storage environment was related to Firmicutes and Proteobacteria, which mainly include Bacillus, Psychrobacter and Atopobium.

Physicochemical properties and antibacterial mechanism of TP microcapsules/LZM-PVA gradual sustained-release composite coatings

Tea polyphenol (TP) has excellent preservation effect on the aquatic product, however, its long-term antibacterial and preservation property is poor due to its volatilization. Therefore, a novel sustained –release formulation of TP should be developed for improving the applicability. In this study, the TP microcapsules/LZM-PVA composite coatings with gradual slow release properties were prepared by tape-casting method. Its micro-morphology was characterized and its physicochemical properties were determined. Meanwhile, the antibacterial properties and mechanism of the composite coatings were studied with Pseudomonas fluorescens and Shewanella putrefaciens, the dominant spoilage bacteria in aquatic products, as the objects. The results show that the addition of TP and other substances affects the structure of PVA coatings, and changes the intermolecular force of PVA, the coatings is wrinkled and denser, which effectively improve the mechanical properties of the PVA coatings, and finally lead to the decrease of air permeability. Among them, the TP microcapsules/LZM-PVA composite coating has the best mechanical properties, the least amount of CO2 and water vapor penetration. The results of antibacterial experiments show that the PVA coating without preservatives has no antibacterial property. Compared with the bacterial cells treated by the corresponding composite coatings without LZM, the integrity of the cell membrane is poor and the permeability is higher after treated by the composite coating with LZM, which is due to the synergistic antibacterial effect of TP and LZM. More importantly, when TP is replaced by TP microcapsules, the antibacterial ability of the composite coatings is poor at the initial stage. However, TP is embedded in the space network structure formed by CS-sodium tripolyphosphate. TP in the coatings can be released slowly from microcapsules to coatings, and then from coatings to the culture medium, which prolong the antibacterial effect time and cause continuous damage to the bacteria. Moreover, the chitosan which is the wall material of TP microcapsules also has a certain antibacterial effect. So the TP microcapsules/LZM-PVA coating could be an ideal choice in the food preserving.

Characterization of the Volatiles and Quality of Hybrid Grouper and Their Relationship to Changes of Microbial Community During Storage at 4 °C.

To investigate the effects of spoilage bacteria on aquatic product quality and volatile organic compounds (VOCs) in hybrid grouper (Epinephelus fuscoguttatus ♀×Epinephelus lanceolatus ♂), the physical conditions were evaluated, the chemical changes including color, total volatile base nitrogen (TVB-N), VOCs, and free amino acids (FFAs) were determined, and biological profiles were made through microbial community (total viable counts (TVC), 16S rRNA gene amplification sequencing, and next-generation sequencing (NGS) technology on hybrid grouper, which were stored at 4 °C for 10 days. The results showed that the whiteness and TVB-N of grouper increased throughout the storage period. The contents of glycine, alanine, and total free amino acid decreased with the microbial activity towards the end of the study period. At the end of storage, the TVC reached 9.0 log10 (CFU/g). Seventy eight strains of bacteria were isolated from the hybrid grouper, most of which were shown to be Pseudomonas spp., after 16S rRNA sequencing. The results of the NGS test showed that the diversity of dominant bacteria decreased with time; Pseudomonas azotoformans was the dominant spoilage bacteria at the end of storage. The VOCs of fish and bacteria in the grouper’s spoilage process were presented in headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS). Twenty eight compounds were identified in hybrid grouper, among which alcohol and aldehyde were used to characterize freshness, both of which were not only related to the overall flavor of the grouper, but were also affected by microbial activity. However, due to the complexity of microbial communities in aquatic products, the correlation between community changes and VOCs needs further research. This study provides insights into the correlation between VOCs and specific spoilage organisms (SSOs) through the analysis of the microbial community and VOCs.

Isolation and Identification of Dominant Spoilage Bacteria in Refrigerated Catfish Fillets

In order to discuss the species of dominant spoilage bacteria in refrigerated 7 d catfish fillets,the squid was taken in a 4℃ sterile cold storage and placed in a vacuum oven at 4℃ for 7 days. Three strains of bacteria,numbered x1-1,y1-1,and y2-1,were isolated from the corrupted fish meat for bacterial morphology observation,physiological and biochemical tests,and 16S rDNA sequence determination.The results showed that all the strains were Gram-negative Brevibacterium spp,and both were facultative anaerobic bacteria. The results of sequencing and phylogenetic tree analysis showed that x1-1 was closely related to Aeromonas hydrophila,reaching 99.9%. The relationship between y1-1 and Aeromonas veronii was up to 99.79%;y2-1 was similar to Aeromonas allosaccharopila,reaching 99.8%.Combined with the above research results,x1-1 is A.hydrophila;y1-1 is A.veronii;y2-1 is A. allosaccharophila.In summary,the dominant spoilage bacteria in refrigerated catfish fillets is Aeromonas.

Products Analysis and Molecular identification of Flavonoids-Produce Endophytic fungi in Ginkgo Biloba

Endophytic fungi (Y6, Y8, Y10, G8) of ginkgo were studied in this paper to clarify what species of them, what kind of flavonoids of their metabolite, and the bacteriostatic activity of fermentation liquid from endophytic fungi. Disc diffusion method was used to determine antibacterial properties that the target strains to dominant spoilage bacteria X15 (bacillus), T10 (proteus), X5 (aureus), N4 (Serratia marcescens) from low temperature meat products, the results showed that Y6, Y8 and Y10 had best strains antibacterial properties for X15, T10, N4, respectively, and G8 is the best strain in antibacterial performance. The metabolites of four endophytic fungi of ginkgo biloba were analysed by high performance liquid chromatography (HPLC), the results showed that quercetin and isorhamnetin were contained in the fermented liquid of Y6 strain, isorhamnetin and quercetin were contained in the fermented liquid of Y8 and Y10 respectively. Four strains were identified by molecular biology by extracting DNA, the result shows that Y6, Y8, Y10, G8 strains were Penicillium sp., Dothiorella gregaria., Phoma sp., Fusarium nematophilum.

Effects of different salt concentrations and vacuum packaging on the shelf-stability of Russian sturgeon (Acipenser gueldenstaedti) stored at 4 °C

The effects of different salt concentrations and vacuum packaging on the quality and microbiota dynamics of Russian sturgeon fillets stored at 4 °C were evaluated over a 12-day storage in this study. During refrigerated storage, The combination of 6% (w/v) brine salting for 2 h and vacuum packaging exerted beneficial effects on the quality of Russian sturgeon fillets, as demonstrated by affecting the sensory acceptability, retarding the production of total volatile basic nitrogen (TVB-N), delaying lipid oxidation measured by thiobarbituric acid reactive substances (TBARS) value. Meanwhile, the morphological changes in the muscle at different salt concentrations were observed by Scanning Electron Microscopy (SEM). Based on total viable counts (TVC), there was a lag phase of 3 days for the shelf life of 6% salting samples and vacuum packaging samples compared with the control. Moreover, the microbiota variability in different groups was investigated. The combination of 6% salting and vacuum packaging could effectively delay the growth of Pseudomonas which was the predominant microbiota in Russian sturgeon fillets during the final period of storage. The results indicated that 6% salting combined with vacuum packaging extended the shelf-life of Russian sturgeon fillets during storage, which was mainly due to their inhibition on dominant spoilage bacteria.

Combined propidium monoazide pretreatment with high‐throughput sequencing evaluated the bacterial diversity in chicken skin after thermal treatment

The purpose of this experiment was to study the bacterial diversity and predominance of spoilage bacteria in chicken skin at different thermal treatment temperatures (60, 70, 80, 90, 100, 110, 120°C). Bacteria in chicken skin was collected, then propidium monoazide treatment to remove the DNA of dead cell, total DNA was extracted by Tiandz Bacterial DNA Kit, and investigated by high-throughput sequencing of the v3/v4 regions of the 16S rDNA gene. A total of 796008 high-quality bacterial sequences were obtained for assessing the microbial diversity of chicken skin from seven thermal treatment group and control group. The results showed that the bacterial diversity in chicken skin at 90°C was lowest. And Acinetobacter (25·88%), Clostridium (20·70%), Bacteroides (13·93%) and Myroides (13·13%) were the main flora at 25°C; The Clostridium was dominant genus of the samples heat-treated by 60, 70, 80 and 90°C, the proportion of this genus were up to 64·86, 77·42, 52·22 and 87·30% respectively. The Bacillus was the main flora of the samples heat-treated by 100, 110 and 120°C, and the relative percentages were 39·44, 79·61 and 45·96% respectively. In addition, high-temperature-resistant Serratia was found in chicken skin. The study revealed that the relationship between thermal treatment temperature and bacterial diversity and dominant spoilage bacteria in chicken skin, which had a strong guiding significance for the control and prediction of micro-organisms in foods. The results of this paper could provide a theoretical basis for meat products containing chicken skin, including the safe use of chicken skin, determination of sterilization process parameters and selection of preservatives for compounding, which has strong practicality in China.

Antibacterial properties and possible action mechanism of chelating peptides-zinc nanocomposite against Escherichia coli

Octopus scraps, as a kind of marine waste, have drawn much attention due to its biological values. Amino groups and carboxyl groups of octopus scraps peptides (OSP) chelated with Zn2+ formed OSP-Zn by Zn-N and Zn-O covalent bonds. The aggregation state of OSP had been changed and the typical particle diameter of OSP transformed from 104.74 nm to 147.36 nm after chelating with zinc. The chelate OSP-Zn showed notably antimicrobial ability towards Escherichia coli (E. coli). Moreover, the antibacterial mechanism of OSP-Zn against E. coli might be explained by the pathway of damaging cell membrane structure and oxidative stress-mediated apoptosis. It also suggests that OSP-Zn could inhibit the growth of the dominant spoilage bacteria of Penaeus vannamei and exhibit a good preservative effect. Our work illuminates the synergic effect of OSP and Zn complexes for the first time, supporting the potential application of OSP-Zn chelate as a natural bacteriostatic agent in the food or pharmaceutical industry.

Amplification of Raman spectra by gold nanorods combined with chemometrics for rapid classification of four Pseudomonas

This paper demonstrates the application of surface-enhanced Raman scattering (SERS) using positive charged gold nanorods (Au NRs) as an enhancement substrate to classify Pseudomonas spp. coupled with multivariate methods. Four species of Pseudomonas as dominant spoilage bacteria of food were isolated from rotten chicken, namely, Pseudomonas gessardii (P9), Pseudomonas psychrophila (P8), Pseudomonas psychrophila (S2) and Pseudomonas fluorescens (T3). Au NRs were synthesized with positive charge by seed-mediated growth method which can be adsorbed onto the surface of the bacteria by electrostatic adsorption. SERS spectra were collected individually for four types of Pseudomonas and pretreated by mean centering (MC), then principal component analysis (PCA) and hierarchical clustering analysis (LDA) were used to achieve data dimensionality reduction and visualize the result of differentiation for the species of Pseudomonas. Particularly, the classification accuracy of LDA was reached to 100%. Following we applied hierarchical clustering analysis (HCA) to cluster each species of Pseudomonas and the results of HCA consistent with the results of 16S rRNA. This study has shown that SERS combined with LDA and HCA can be used as a reliable method to classify Pseudomonas.

Effect of storage temperature on bacterial diversity in chicken skin.

The purpose of this experiment was to study the bacterial diversity and predominance of spoilage bacteria in chicken skin at different storage temperatures (4, 25 and 37°C). The total bacteria in chicken skin were collected, total DNA was extracted by an E. Z. N. A. Bacterial DNA Kit, and the v3-v4 regions of the 16S rDNA gene in the microbiota of the chicken skin were studied using the Illumina Hiseq platform. A total of 91862 bacterial sequences were obtained for assessing the microbial diversity from chicken skin at three storage temperatures. The results showed that the bacterial diversity in chicken skin at 25°C was the highest, and Pseudomonas was dominant at 4°C, while Acinetobacter and Clostridium were the main flora at 25°C. Clostridium dominated and played a critical role in the chicken skin stored at 37°C. The effect of temperature on bacterial diversity in chicken skin was significant and the dominant spoilage bacteria were different in chicken skin at different temperatures, which had a strong guiding significance for the control and prediction of micro-organisms in foods. The results of this article could provide a theoretical basis for meat products containing chicken skin, including the safe use of chicken skin, determination of sterilization process parameters and selection of preservatives for compounding.

Rapid Pseudomonas Species Identification from Chicken by Integrating Colorimetric Sensors with Near-Infrared Spectroscopy

Pseudomonas spp. are the dominant spoilage bacteria which can cause chicken spoilage. Some traditional detection methods are often unsuitable for their rapid real-time detection. Thus, in this paper, a fusion strategy based on colorimetric sensors and near-infrared spectroscopy was applied to rapidly identify Pseudomonas spp. in chicken. First, four different species of Pseudomonas—Pseudomonas gessardii, Pseudomonas psychrophila, Pseudomonas fragi, and Pseudomonas fluorescens—were isolated from putrid chicken, and then, the odor and spectral information of the Pseudomonas species and their mixture were obtained by colorimetric sensors and near-infrared spectroscopy, respectively. Thirty-six odor characteristic variables and 33 spectral characteristic variables were extracted from each technique and used for data fusion based on principal component analysis (PCA). Back-propagation artificial neural network (BP-ANN) was used to build identification model for the discrimination of the different Pseudomonas species. The results showed that the discrimination capability of the model based on data fusion was superior to that based on the two techniques independently, and eventually BP-ANN achieved 100% classification rate by cross-validation and 98.75% classification rate in predication set. This work indicates that the combination of colorimetric sensors and near-infrared spectroscopy is promising for the rapid identification of Pseudomonas species in chicken extract, and hence may be applied towards quality monitoring.

Identification of spoilage bacteria using a simple colorimetric sensor array

This paper demonstrates the application of a simple colorimetric sensor array response to the problem of identifying spoilage bacteria with the help of multivariate calibration. Four dominant spoilage bacteria from meat products, namely, Pseudomonas koreensis PS1, Bacillus fusiformis J4, Acinetobacter guillouiae P3, and Enterobacter cloacae P5, were tested in the study. We developed a novel colorimetric sensor array by printing 15 chemically responsive dyes (9 metalloporphyrins and 6 pH indicators) on a C2 reverse silica-gel flat plate. According to the chemical dyes response to volatile organic compounds (VOCs) produced by bacteria, a colorific change profile was obtained. We attempted multivariate calibrations to classify four bacterial strains, and linear discriminant analysis (LDA) achieved a good classification result by leave-one-out cross-validation. Besides, we systemically studied the internal relationship among four bacterial strains using this proposed method with the help of hierarchical cluster analysis (HCA). And HCA results using the proposed method are in agreement with the results using 16S rRNA sequences analysis. This work has demonstrated that the novel sensor array has a high potential for reliable identification of meat spoilage bacteria grown on solid media and on Petri dishes.

Research on Discrimination of Dominant Spoilage Bacteria in Pork Based on Natural Gas-Sensing Material

Research on Discrimination of Dominant Spoilage Bacteria in Pork Based on Natural Gas-Sensing Material

Evaluation of the spoilage potential of bacteria isolated from spoiled raw salmon (Salmo salar) fillets stored under modified atmosphere packaging

The spoilage potential of eight bacterial groups/species (Serratia spp., Hafnia alvei, Brochothrix thermosphacta, Carnobacterium maltaromaticum, Shewanella baltica, Lactococcus piscium, Photobacterium phosphoreum, “other Enterobacteriaceae” [containing one strain of Moellerella sp., Morganella sp. and Pectobacterium sp.]) isolated from spoiled raw salmon fillets stored under modified atmosphere packaging (MAP) was evaluated by inoculation into sterile raw salmon cubes followed by storage for 12days at 8°C. Microbial growth and sensory changes were monitored during the storage period. The dominant spoilage bacteria were C. maltaromaticum, H. alvei and P. phosphoreum. In order to further characterize their spoilage potential and to study the effect of their interactions, each of these 3 specific spoilage organisms (SSO) and two mixed-cultures, C. maltaromaticum/H. alvei and C. maltaromaticum/P. phosphoreum were tested in the sterile salmon model system using a combination of complementary methods: molecular (PCR-TTGE), sensory, chemical and conventional microbiological analyses. It was concluded that, in the mixed-culture inoculated samples, the dominant species determined the spoilage characteristics. The volatile fraction of P. phosphoreum inoculated samples was analyzed by solid-phase microextraction (SPME) followed by gas chromatography coupled to mass spectrometry (GC–MS). Among the specific volatile compounds present on P. phosphoreum spoiled inoculated samples, acetic acid was correlated with sensory analysis and can be proposed as a raw salmon spoilage marker.

Bacterial diversity and spoilage-related microbiota associated with freshly prepared chicken products under aerobic conditions at 4°C.

This study analyzed the bacterial diversity and spoilage-related microbiota associated with freshly prepared chicken products stored aerobically at 4°C, using "bone and chicken string," a product popular in the People's Republic of China, as the study subject. Samples collected from three different factories were tray packaged with cling film and stored at 4°C. Bacterial diversity and dominant bacteria were analyzed using PCR amplification and denaturing gradient gel electrophoresis. Combined with selective cultivation of the dominant bacteria and correlation analysis, the dominant spoilage microbiota was determined. The results showed that bacterial diversity varied with different manufacturers. Such bacteria as Acinetobacter sp., Carnobacterium sp., Rahnella sp., Pseudomonas sp., Brochothrix sp., and Weissella sp. were detected in freshly prepared chicken products during storage. And Carnobacterium sp., Pseudomonas sp., and Brochothrix sp. bacteria were the common dominant spoilage bacteria groups in most freshly prepared chicken products from different factories. Carnobacterium was, for the first time, shown to be an important contributor to the spoilage-related microflora of freshly prepared chicken products stored aerobically under refrigeration. Our work shows the bacterial diversity and dominant spoilage microbiota of freshly prepared chicken products stored aerobically under refrigeration.

Estimation of Shelf-life of Frankfurter Using Predictive Models of Spoilage Bacterial Growth

The aim of this research was to develop predictive models for the growth of spoilage bacteria (total viable cells, Pseudomonas spp., and lactic acid bacteria) on frankfurters and to estimate the shelf-life of frankfurters under aerobic conditions at various storage temperatures (5, 15, and <TEX>$25^{\circ}C$</TEX>). The primary models were determined using the Baranyi model equation. The secondary models for maximum specific growth rate and lag time as functions of temperature were developed by the polynomial model equation. During 21 d of storage under various temperature conditions, lactic acid bacteria showed the longest lag time and the slowest growth rate among spoilage bacteria. The growth patterns of total viable cells and Pseudomonas spp. were similar each other. These data suggest that Pseudomonas spp. might be the dominant spoilage bacteria on frankfurters. As storage temperature increased, the growth rate of spoilage bacteria also increased and the lag time decreased. Furthermore, the shelf-life of frankfurters decreased from 7.0 to 4.3 and 1.9 (d) under increased temperature conditions. These results indicate that the most significant factor for spoilage bacteria growth is storage temperature. The values of <TEX>$B_f$</TEX>, <TEX>$A_f$</TEX>, RMSE, and <TEX>$R^2$</TEX> indicate that these models were reliable for identifying the point of microbiological hazard for spoilage bacteria in frankfurters.